In the accumulation conveyor field it has long been desired to have a unit which can handle large, heavy articles and small, light articles on the same unit.
In prior accumulation conveyors where the force required to discontinue the conveyor drive when an article was stopped on the unit and to start the drive when the stopped article again should move has usually been provided a sensor operated either by the weight or movement of an article, or by both.
This meant that small or light articles could not operate a clutch or the like of sufficiently heavy duty for the conveyance of heavy articles so that light and heavy articles could not be mixed unless some extraneous power such as air or electricity was resorted to which required complicated mechanisms, was expensive and required space and much maintenance. An example of such a unit is disclosed in U.S. Pat. No. 3,225,893.
Efforts have been made to produce accumulation conveyors in which the power required to operate the clutches to continue or discontinue the movement of articles is provided by the conveyor drive which moves the articles conveyed, but to date such equipment has been so complicated as to be prohibitively expensive, undependable, require extensive adjustment, other maintenance, or all of these undesirable factors. Examples of such units are disclosed in U.S. Pat. Nos. 3,219,172; 3,285,391; 3,156,345; 3,116,823; 3,164,246; 3,206,008; 3,136,406, and 3,232,415.